1. Field of the Invention
This invention relates generally to an antenna for a vehicle tire interrogation system that interrogates a tire sensor and, more particularly, to an antenna for a hand held reader for a vehicle tire interrogation system that is able to interrogate a tire pressure sensor and a radio frequency identification (RFID) sensor.
2. Discussion of the Related Art
Heavy trucks and other vehicles are extensively used to transport passengers and goods. These trucks sometimes include eighteen or more tires, creating a large-scale tire tracking challenge. An efficient tire tracking system would speed up inventory and delivery of tires, and also keep statistics on each tire in use, such as pinpointing old or overused tires, before blowouts or other failures occur.
The Michelin Corporation has initiated such a tire tracking system for this purpose. The Michelin tire tracking system embeds RFID sensors and temperature and pressure sensors in some of its tires, which are monitored by an RF interrogation system. The interrogation system includes a remote drive-by unit (DBU) including suitable antennas that interrogate the RFID sensors as the truck, or other vehicle, drives slowly down a particular roadway. In one design, four rows of antennas are strategically placed in the roadway so that all of the inner and outer tires of the truck are interrogated by the system.
The tires include surface acoustic wave (SAW) temperature and pressure sensors and an RFID sensor including a serial number and other information. The interrogation system illuminates the sensors with an RF signal, which causes the sensors to radiate a low frequency, RF signal encoded with a tire ID, temperature, pressure and other information. The temperature and pressure sensors operate at about the 434 MHz frequency band and the RFID sensor operates at about the 915 MHz frequency band.